Friday, 14 February 2014

Eyes wide shut

The last few weeks have mostly been spent going through lots of data writing up a report on the effects of mydriatics and cycloplegics, in particular tropicamide and cyclopentolate. I am sure most optometry students and practitioners will be familiar with what they are used for but for those who don't here is a quick recap:

Tropicamide is mainly used to dilate the pupil to allow the practitioner a better view of the retina at the back of your eye especially to see the periphery, to check for haemorrhages, detachments and other serious pathologies. It works by relaxing the iris muscle sphincter.

Cyclopentolate also dilates the pupil but it's main function is to relax accommodation, the ability to focus on close up objects. This is needed to determine full refractive error in young children who have high accommodation levels; in latent hypermetropes - people who are unable to fully relax their accommodation and for preliminary testing for laser surgery. Cyclopentolate works in a similar way to tropicamide but also paralyses the ciliary muscle which controls accommodation. The downside is that it takes longer to wear off so patients are unable to read for several hours afterwards and may be sensitive to bright lights.

Here is a great video of someone looking at their own fundus using a lens and a mobile phone after they have been dliated. This is just the central fundus but can view periphery with other techniques.
Self fundus exam video

The drugs do sting a little bit when they are put in but they are only put in when they are needed, so if an optometrist suggests you are dilated it is for a good reason and it is advised you go ahead with it.
Before these drugs were invented other methods were used primarily to make the eyes look wide and beautiful, these included cocaine - dilated peoples are one of the more obvious signs that someone has taken cocaine. The plant Belladonna, also known as deadly nightshade, was also used by women in the Middle Ages to dilate their pupils to make them look more attractive. Personally having dilated pupils doesn't feel attractive, it gives me a slightly wide eyed and scary look.

Not all dilated pupils are due to drug use, either illegal or ophthalmic. Some are also caused by nerve damage, like the case of David Bowie, whose left eye is permanently dilated after he suffered an injury in a fight when he was young.

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